Besides women changing their surname after marriage, many others change their name/surname for varied reasons like astrology, better suitability, simplifying long names etc.
The first step is to create an affidavit which may be sworn in before a Judicial Magistrate First Class or even a Notary public. The next step is to make public announcement. An advertisement must be published declaring change of name in one English and one Regional newspaper. The final step is the Gazette Notification. All the three steps are mandatory. After Central/State gazette notifies the change, the new name can be used for all purposes.